Linking habitat characteristics with juvenile density to quantify Salmo salar and Salmo trutta smolt production in the river Savaran, Sweden

P>Habitat mapping along 85 km of river was related to juvenile (15 years of electric fishing) and smolt (3 years of screw-trapping) abundance data to estimate salmon, Salmo salar L., and sea trout, Salmo trutta L., smolt production in the River Savaran, northern Sweden. Spawning site selection by radio-tagged salmon (n = 12) and sea trout (n = 4) was also assessed. Fifty-one hectares of potential spawning and nursery habitat was found in the main stem river, representing 25% of the total river area. These areas were estimated to yield 1300-7580 salmon and 630-3540 sea trout smolts based on juvenile densities, equating with 3 years of screw-trap data (2990-5080 salmon and 680-2520 trout smolts, respectively). A hypothetical maximum production of about 19 900 salmon smolts was predicted for the river at a density of 40, 0+ salmon 100 m-2. Tracking adults during the spawning period identified optimal and potential reproductive areas.